Steering wheel

ABSTRACT

A steering wheel including a core metal of a ring portion also includes a soft portion and a hard portion for covering circumferential portions of the core metal. Leather is disposed on a surface of the soft portion and overlaps edges of the hard portion. Extended portions extending from the soft portion surround the core metal and are covered by the hard portion. In this manner, a user of the steering wheel may experience comfort in the feel of the leather on the soft portion as well as an aesthetically appealing hard portion.

The present application is a continuation of U.S. application Ser. No.10/093,891, filed on Mar. 11, 2002, entitled STEERING WHEEL, nowabandoned, which is a division of U.S. application Ser. No. 09/429,927,filed on Oct. 29, 1999, entitled STEERING WHEEL (now granted U.S. Pat.No. 6,386,063), which is based upon and claims the benefit of JapanesePatent Application Nos. Hei. 10-311382, 10-373665, 10-373648, 10-373567,and 10-373533, the contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a steering wheel for steering avehicle, and more particularly to a steering wheel incorporating a coremetal of an annular ring portion, which is held when steering isperformed, structured such that a hard portion made of hard syntheticresin and a soft portion made of soft synthetic resin softer than thehard portion are disposed around the core metal such that the hardportion and the soft portion are disposed in the planar circumferentialdirection of the ring portion.

2. Description of the Related Art

Hitherto, a portion of steering wheels has a structure that a hardportion made of hard synthetic resin or a woody material and a softportion made of soft synthetic resin softer than the hard portion aredisposed around a core metal of an annular-ring portion which is heldwhen steering is performed such that the hard portion and the softportion are disposed in the planar circumferential direction of the ringportion.

Hitherto, a portion of wood steering wheels each having a woodgrainfinish has a structure that woody members are partially bonded to theouter surface of the ring portion. Another portion has a structure thata woody member is provided for the overall circumference of the ringportion by molding.

The conventional steering wheel of the foregoing type is structured suchthat the hard portion made of the hard synthetic resin or the woodymaterial is partially bonded to the core metal of the ring portion inthe planar circumferential direction. When the foregoing type steeringwheel is arranged such that the hard portion formed in the planarcircumferential direction of the ring portion by a bonding operation andthe soft portion formed to cover the core metal of the ring portion by amolding operation, such as injection molding are provided, the followingproblem arises.

That is, when the steering wheel of the foregoing type is manufactured,the soft portion is molded before the hard portion is bonded to preventformation of burrs of the soft portion on the surface of the hardportion. When the soft portion is molded, a dimensional error of thecore metal sometimes inhibits the core metal of the ring portion to bedisposed in the central portion of the cross section of the cavity ifthe core metal of the ring portion is introduced into the mold. If thesoft portion is molded and the hard portion is then bonded to the coremetal of the ring portion in a state where the deviation of theforegoing type occurs, unnecessary stepped portion 204 occurs betweenthe hard portion 202 and the soft portion 203, as shown in FIG. 28. Thereason for this will now be described. For example, the upper and lowerhard portions 202 bonded to the core 201 of the ring portion can bedisposed without any deviation from the core metal 201, as shown in FIG.29. Since the soft portion 203 covering the core metal 201 is deviatedfrom the core metal 201, a stepped portion 204 is formed between thehard portion 202 and the soft portion 203. The foregoing stepped portion204 deteriorates the quality of the design of the appearance of the ringportion R. As a result, there arises a problem in that a defectivesteering wheel is produced.

The foregoing steering wheel is manufactured by bonding the hard portionto a portion around the core metal of the ring portion. A portion of thesteering wheels has a structure that both of the hard portion and thesoft portion are formed by injection molding. A steering wheel of theforegoing type and the conventional problem will now be described.

The steering wheel of the foregoing type has a structure that a hardportion made of hard synthetic resin and a soft portion made of softsynthetic resin softer than the hard portion are disposed around thecore metal of the ring portion constituted by a steel pipe such that thehard portion and the soft portion run in the planar circumferentialdirection of the ring portion. The hard portion is disposed at each ofthe front and rear portions of the steering wheel. Each of the portionsof the hard portion is made of hard synthetic resin, such as foamedepoxy resin which covers the core metal of the ring portion. On theother hand, the soft portion is disposed in each of the right and leftportions of the steering wheel, the soft portion being made of foamedurethane which covers the portion around the core metal of the ringportion.

Note that the surface of the hard portion has a thin cover formed into awoodgrain finish. The surface of the soft portion has a leather cover.

The foregoing steering wheel is manufactured such that the core metal ofthe steering wheel is manufactured. Then, the core metal of the steeringwheel and the cover are introduced into a mold for molding the hardportion. The front and rear hard portions are collectivelyinjection-molded. Then, the right and left soft portions arecollectively. injection-molded. Then, the leather member is wound aroundthe soft portion.

If the steering wheel of the type having the hard and soft portionsdisposed in the planar circumferential direction of the ring portion is,for a long time, allowed to stand in the cabin of a vehicle, thetemperature of which is raised, a crack sometimes occurs in the hardportion. The reason for this lies in that the coefficient of thermalexpansion of the core metal of the ring portion made of the steel pipeand that of the hard portion are considerably different from each other(the core metal of the ring portion has a small coefficient of thermalexpansion and the hard portion has a large coefficient of thermalexpansion). Also the soft portion and the core metal of the ring portionare greatly different from each other in the coefficient of thermalexpansion. Since the soft portion made of the soft material is able toabsorb the difference in the coefficient of thermal expansion by elasticdeformation and the like, cracks cannot easily occur.

When the hard portion is made of a low-cost polypropylene or ABS resin,the coefficient of thermal expansion of the foregoing low-cost materialis made to be furthermore different as compared with the foamed epoxyresin. Therefore, there arises a problem in that the crack easilyoccurs.

In general, the foregoing steering wheel is structured such that thevolume of the front portion of the front and rear portions which arecollectively formed by injection molding is made to be larger than thevolume of the rear portion.

Therefore, the molding operation is performed such that injection of thematerial for molding into the cavity for molding the rear hard portionis completed prior to completion of injection of the material formolding into the cavity for molding the front hard portion.

As a result, there arises a problem in that a large burr is formedadjacent to the rear hard portion as compared with the portion adjacentto the front hard portion. Therefore, there arises a problem in that anexcessively large labor is required to remove the burr.

When the hard portion of the ring portion is formed, the conventionalsteering wheel has been molded such that one of gates arranged to injectthe material for molding into the cavity of the mold and disposed at theend of the hard portion in the planar circumferential direction of thering portion is employed, the one of the gates being disposed at avertical-directional intermediate position of the steering wheel on thecross section of the ring portion.

The hard portion of the ring portion of the foregoing steering wheel issometimes formed such that the gate for injecting the material formolding into the cavity of the mold is, as one of gates disposed at theends in the planar circumferential direction of the ring portion,disposed at an intermediate position in the vertical direction of thesteering wheel on the cross section of the ring portion. In theforegoing case, there arises a problem in that a weld mark is formed onthe upper surface.

The core metal of the ring portion is sometimes formed by die-casting asa substitute for the steel pipe to form an inverted U-shape crosssection. When the gate for molding is disposed at the intermediateposition in the vertical direction of the steering wheel of the crosssection of the ring portion in the foregoing case, the material formolding easily flows along the inner surface of the core metal of thering portion. Thus, the material for molding is injected into the innersurface portion of the core metal of the ring portion. Then, thematerial for molding is injected into the upper surface portion of thecore metal of the ring portion from the lower end portions of the twoside wall portions of the cross section of the core metal of the ringportion. Therefore, a weld mark is furthermore easily formed in theupper surface portion of the core metal of the ring portion.

If the weld mark is formed in the upper surface portion, an individualcoated film or the like must be formed afterwards. Since the uppersurface portion is a portion which is directly observed when thesteering wheel is used, the quality of the appearance of the ringportion of the steering wheel deteriorates if the foregoing coated filmor the like is not provided. When a glossy coated film having a smallthickness is formed, the weld mark is sometimes undesirably highlighted.

A support portion for supporting the inner surface of the leatherportion bonded to the surface of the soft portion is formed at an end ofthe hard portion of the steering wheel of the foregoing type. Moreover,woodgrain grooves into which the ends of the leather portion areinserted are formed in the base portions of the support portion.

The leather portions are sewed together in the inner surface portion ofthe ring portion and, as well as bonded to the soft portion. Moreover,the inner surface of each end portion is supported by the outer surfaceof the support portion of the hard portion. In addition, the ends areinserted into the woodgrain grooves so as to be secured to the hardportion.

The reason why the major portion of the leather portion is provided forthe soft portion lies in that a satisfactory touch can be realized inthe foregoing case when the foregoing portions are held by the hands.

The reason why the ends of the leather portions are supported by thehard portions lies in that sags of the ends of the leather portion canbe prevented in the foregoing case.

When the conventional steering wheel around which the leather is woundis manufactured, the core metal of the steering wheel is manufactured.Then, the core metal of the steering wheel and the coating member areintroduced into the mold for molding the hard portion. Thus, the hardportion is molded. Then, the soft portion is molded, and then theleather is wound around the soft portion so as to be sewed and bonded tothe soft portion. Then, the ends of the leather are supported by theouter surface of the support portion of the hard portion. In addition,the ends of the leather are inserted into the woodgrain groove.

The structure that the ends of the leather are inserted into thewoodgrain groove to secure the leather to the hard portion, however,encounters a problem in that the end of the leather is separated fromthe woodgrain groove when the leather has been contracted owing to useof the steering wheel for a long time. Thus, there is apprehension thatthe appearance of the ring portion deteriorates.

SUMMARY OF THE INVENTION

To solve the foregoing problems, a first object of the present inventionis to provide a steering wheel with which formation of an unnecessarystepped portion between the hard portion and the soft portion can beprevented and which is capable of improving the appearance of the ringportion.

A second object of the present invention is to provide a steering wheelwhich is capable of preventing formation of a crack of a hard portion ifthe ring portion is structured such that the hard portion and a softportion are provided for the steering wheel.

A third object of the present invention is to provide a steering wheelwhich can be manufactured such that formation of a burr can be preventedwhen a plurality of coating portions having different volumes aresectioned and provided in the planar circumferential direction of thering portion and when the plural coating portions are collectivelyformed by injection molding.

A fourth object of the present invention is to provide a steering wheelwhich is capable of formation of a weld mark in the upper surfaceportion of a core metal of a ring portion thereof when a coating layerpartially disposed in the planar circumferential direction of the ringportion and made of synthetic resin is formed by injection molding byusing one gate disposed at an end of the coating layer.

A fifth object of the present invention is to provide a steering wheelaround which leather is wound, with which ends of the leather are firmlysecured to a support portion of a hard portion and which is capable ofpreventing occurrence of a defect in the appearance of the ring portioneven after the steering wheel has been used for a long time.

According to the present invention, there is provide a steering wheelcomprising: a core metal of a ring portion thereof; a soft portionformed by molding to cover the core metal of the ring portion; anextended portion integrally extended from the soft portion to surroundthe core metal of the ring portion; and a hard portion which is bondedto the upper surface of the extended portion and which is harder thanthe soft portion.

The steering wheel according to the present invention has the extendedportion extended from the soft portion and formed at the position atwhich the hard portion is bonded. That is, when the soft portion isformed around the core metal of the ring portion by molding, also theextended portion is formed. If the extended portion is deviated from thecore metal of the ring portion, the hard portion, which is bonded to theportion around the extended portion, is not deviated. That is, the hardportion can be provided for the ring portion.

The extended portion is molded integrally with the soft portion in theportion around the core metal of the ring portion. If the formedextended portion is deviated from the core metal of the ring portion,any deviation from the soft portion can be prevented in the planarcircumferential direction of the ring portion. As a result, the softportion and the hard portion bonded to the portion around the extendedportion can be disposed without any deviation in the planarcircumferential direction of the ring portion.

Therefore, when the hard portion bonded around the cross sectionalcircumference of the ring portion and the soft portion formed to coverthe core metal of the ring portion by molding are provided in the planarcircumferential direction of the ring portion, the steering wheelaccording to the present invention is able to prevent formation of anunnecessary stepped portion between the hard portion and the softportion. As a result, the appearance of the ring portion can beimproved.

The steering wheel according to the present invention incorporates thesoft portion and the extended portion made of the same material andprovided for the overall circumference in the planar circumferentialdirection of the ring portion to cover the core metal of the ringportion. Therefore, a necessity for performing an operation for cuttingburrs of the soft portion can be eliminated. Therefore, the number ofman-hours and manufacturing cost can be reduced. That is, as shown inFIGS. 28 and 29, the conventional structure is formed such that a softportion 203 is formed apart from the position at which a hard portion202 is disposed. Therefore, burrs formed in the bonding portion, allowedto adhere to the outer surface of the core metal of the ring portion 201and extending from the soft portion 203, must be removed before the hardportion 202 is bonded after the soft portion 203 has been formed.

The steering wheel according to the present invention comprises: a coremetal of a ring portion thereof; a hard portion disposed around the coremetal of the ring portion; and a soft portion which is disposed aroundthe core metal of the ring portion and which is softer than the hardportion. The hard portion and the soft portion are disposed in theplanar circumferential direction of the core metal of the ring portion.The core metal of the ring portion has an inverted U-shape crosssectional shape and made of a die-cast metal.

The steering wheel according to the present invention has the core metalof the ring portion made of the die-cast metal. The general-purposedie-cast metal material for use in the die-cast operation is a lightalloy, such as an aluminum alloy or a magnesium alloy. Each of theforegoing die-cast metal materials has a coefficient of thermalexpansion which is about two times the coefficient of thermal expansionof a conventional steel pipe. Therefore, the coefficient of thermalexpansion of the core metal of the ring portion closes to thecoefficient of thermal expansion of the hard synthetic resin whichconstitutes the hard portion. Therefore, even if the steering wheel isallowed to stand in the cabin of a vehicle, the temperature of which israised excessively, the hard portion cannot easily be cracked.

That is, a die-cast metal material having a coefficient of thermalexpansion of 20×10⁻⁶/° C. or greater is employed to constitute the coremetal of the ring portion. Thus, the coefficient of thermal expansion ofthe core metal of the ring portion can be made to be about two or moretimes the coefficient of thermal expansion of the conventional steelpipe because the conventional steel pipe has a coefficient of thermalexpansion of 12.1×10⁻⁶/° C. Therefore, the coefficient of thermalexpansion of the core metal of the ring portion can be made to be closerto the coefficient of thermal expansion of the hard synthetic resinwhich constitutes the hard portion. Therefore, even if the steeringwheel is allowed to stand in the cabin of a vehicle, the temperature ofwhich is raised excessively, the hard portion cannot easily be cracked.

The core metal of the ring portion has the inverted U-shapecross-section to enlarge the surface area. Therefore, heat conductedfrom the hard portion can easily be absorbed. Moreover, absorbed heatcan be conducted from the core metal of the ring portion to the steeringshaft and the like through the spokes and the core metal of the bossportion of the steering wheel. Thus, the temperature of the hard portioncan easily be lowered. As a result, thermal expansion of the hardportion can be prevented. Hence it follows that a crack of the hardportion can furthermore easily be prevented.

Therefore, when the ring portion of the steering wheel according to thepresent invention is structured such that the hard portion made of thehard synthetic resin and the soft portion made of the soft syntheticresin softer than the hard portion are disposed in the planarcircumferential direction of the ring portion at a position around thecore metal of the ring portion, occurrence of a crack of the hardportion can be prevented.

If the core metal of the ring portion has the inverted U-shape crosssection, the core metal of the ring portion is made of die-cast.Therefore, when the cavity of the die-cast mold is formed to correspondto a required shape, the foregoing cross sectional shape can easily bemaintained.

When the core metal of the ring portion has the inverted U-shape crosssection, another effect can be obtained in that the bending strength ofthe ring portion which is exerted on the axial direction of the steeringwheel can be enlarged.

A method of manufacturing a steering wheel according to the presentinvention is structured such that time at which injection into eachcavity of the mold for forming each coating portion is made to besubstantially the same when the coating portions including the hard andsoft portions sectioned from each other and having different volumes aremolded. Therefore, the operation of the injecting machine for injectingthe material for molding into each cavity of the mold can be interruptedto correspond to time at which injection is completed. When theoperation of the injecting machine is interrupted, no injecting pressureis applied to the inside portion of each cavity. As a result, occurrenceof a burr in the vicinity of each coating portion can be prevented.Hence it follows that an operation for removing burrs which must beperformed after the molding operation has completed can be facilitated.

The resistance of the material for molding which arises when thematerial passes through each runner extending from a sprue of the moldis changed to be inversely proportional to the volume of the coatingportion. That is, the resistance of the material for molding whichpasses through the runner for molding the coating portion having a largevalue is made to be low. On the other hand, the resistance of thematerial for molding which passes through the runner for molding thecoating portion having a small volume is made to be high. Thus, timerequired to complete injection of the material into the cavity formolding the coating portion having the large volume can be shortened. Onthe other hand, time required to complete injection of the material intothe cavity for molding the coating portion having the small volume canbe elongated. Therefore, time required to complete injection of eachmaterial for molding into each cavity of the mold can be made to besubstantially the same.

An accumulating portion for accumulating the materials for molding areprovided for each runner extending from the sprue of the mold formolding the coating portion having the small volume. Thus, noaccumulating portion is provided for the runner for molding the coatingportion having the large volume. Thus, time required to completeinjection of the material into the cavity for molding the coatingportion having the small volume can be elongated because the materialfor molding is accumulated in the accumulating portion. Therefore, timerequired to complete injection of each material for molding into eachcavity of the mold can be made to be substantially the same.

The steering wheel according to the present invention has the structurethat the coating layer including the hard portion and the soft portionwhich are partially disposed in the planar circumferential direction ofthe ring portion is molded by a gate which is used in the moldingoperation and which is disposed above the split surface of the moldedportion in the mold.

Therefore, the material for molding which is used in the moldingoperation conflicts with the upper surface of the core metal of the ringportion when the material has been injected into the cavity through thegate. Therefore, the material flows along the upper surface of the coremetal of the ring portion so as to be charged by a certain quantity inthe upper surface portion of the core metal of the ring portion. Then,the material flows to the lower surface portion of the core metal of thering portion.

Therefore, the weld mark is formed in the lower surface of the coatinglayer. As a result, formation of a weld mark on the upper surface of thecoating layer which deteriorates the appearance of the steering wheelcan be prevented.

Therefore, the steering wheel according to the present invention permitsthe coating layer partially disposed in the planar circumferentialdirection of the ring portion and made of the synthetic resin is formedby injection molding by using one gate disposed at an end of the coatinglayer. Even in the foregoing case, formation of a weld mark on the uppersurface of the core metal of the ring portion can be prevented.

The cross sectional shape of the core metal of the ring portion may beformed to have the inverted U-shape cross section such that the lowerportion of the steering wheel is opened by providing a ceiling wallportion which connects the right and left side walls to each other atthe top ends of the right and left side walls. In the foregoing case,the material for molding which is injected from the gate into the cavitywhen the molding operation is performed conflicts with the upper surfaceof the core metal of the ring portion. Thus, the material flow along theupper surface of the core metal of the ring portion so as to be injectedby a certain quantity in the upper surface portion of the core metal ofthe ring portion. Then, the material flows to the lower surface portionof the core metal of the ring portion. Therefore, if the coating layeris partially formed around the core metal of the ring portion having theinverted U-shape cross section, formation of a weld mark in the uppersurface of the coating layer can be prevented. As a result, a defectiveappearance of the coating layer can be prevented.

When the cross sectional shape of the core metal of the ring portion isformed into the inverted U-shape, the material for molding firstinjected into the inner surface portion of the cross section causes thecore metal of the ring portion to upwards be pushed. Thus, deviation ofthe core metal of the ring portion occurs. The steering wheel accordingto the present invention, however, causes the material for moldinginjected-through the gate disposed above the core metal of the ringportion to downwards push the core metal of the ring portion. Therefore,upward push of the core metal of the ring portion can be prevented. As aresult, the foregoing deviation and deformation of the core metal of thering portion can be prevented.

If a glossy coating film is formed on the surface of the coating layer,no weld mark is formed on the upper surface of the coating layer.Therefore, deterioration in the appearance of the ring portion can beprevented.

When the core metal of the steering wheel is formed by die-casting, thesplit surface of the mold is made coincide with the split surface of thecasting mold for casting the core metal of the ring portion at aposition of the end in the planar circumferential direction of the ringportion of the coating layer. Thus, removal of burr of the coating layercan easily be performed.

That is, when the core metal of the steering wheel is die-cast in such amanner that the core metal of the ring portion has the inverted U-shapecross sectional shape, the casting mold is usually constituted by asplit mold composed of two sections which are opened/closed in thevertical direction of the steering wheel. Moreover, the split surfacesof the two split molds are disposed with reference to the lower endsurface of each of the two side walls on the cross section of the coremetal of the ring portion. When the draft of each of the split molds isconsidered, the inner surface of the cross section of the core metal ofthe ring portion is opened downwards. The outer surface is narrowedupwards.

Therefore, the split surface of the mold is made coincide with the splitsurface of the casting mold in the portion in which burrs are removed.Thus, the lower split mold is forcibly brought into contact with onlythe lower surfaces of the two side walls of the core metal of the ringportion and the inner surfaces of the side wall and the ceiling wall. Onthe other hand, the upper split mold is forcibly brought into contactwith only the outer surfaces of the two side walls and the ceiling wallof the core metal of the ring portion. Thus, the burr-removing surfaceof the split mold of the mold can easily be placed along the draft ofthe core metal of said ring portion.

As a result, the burr-removing surface of the upper and lower split moldis able to completely press the overall circumference of the core metalof the ring portion at the position at which burrs are removed. As aresult, removal of the burrs can satisfactorily be performed.

A case will now be described in which the cross sectional shape of thecore metal of the ring portion is formed into the inverted U-shape tolocate the split surface of the mold is located with reference to asubstantially intermediate portion of the cross section of the coremetal of the ring portion in the vertical direction. In the foregoingcase, the burr-removing surface of the lower split mold cannot beforcibly brought into contact with the outer surface adjacent to thelower ends of the two side walls of the core metal of the ring portion.The reason for this lies in that the draft inhibits forcible contactwith the outer surface because the outer surface adjacent to the lowerends of the two side walls of the core metal of the ring portion arenarrowed upwards. Therefore, a gap is inevitably formed between thelower split mold adjacent to the split surface and the outer surface ofthe two side walls of the core metal of the ring portion. As a result,the material for molding leaks through the gap. Therefore, removal ofburrs cannot satisfactorily be performed.

The steering wheel around which leather is wound according to thepresent invention has the structure that the coating layer for coveringthe hard portion is applied to the outer surface of the support portionincluding a projection portion. Therefore, the soft layer and theleather can be bonded to the hard portion.

That is, the adhesive agent which is applied to the soft portion is aswell as applied to the coating layer of the support portion. Thus, thecoating layer can be used as a primer layer to enable the ends of theleather to be bonded to the hard portion. As a result, the ends of theleather cannot easily be removed from the hard portion. That is, theends of the leather can firmly be secured to the support portion of thehard portion. As a result, occurrence of a defective appearance of thering portion can be prevented.

The coating layer serving as the primer layer for the leather is formedas surface treatment for the hard portion. Therefore, the foregoingcoating layer can be formed by extending the coating. Therefore, thenumber of man-hours and the manufacturing cost of the steering wheel canbe reduced.

The coating layer is also applied to the projection portion projectingtoward the inner surface of the soft portion at a position apart fromthe inner surface of the leather in the support portion in addition tothe support surface for supporting the leather in the support portionfor the hard portion. Therefore, the soft portion can be bonded to thehard portion.

Therefore, contraction of the formed soft portion can be prevented.Thus, separation of the soft portion from the hard portion and the coremetal of the ring portion can be prevented. As a result, deteriorationin the touch when the leather portions are held by the hands can beprevented.

Features and advantages of the invention will be evident from thefollowing detailed description of the preferred embodiments described inconjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings

FIG. 1 is a plan view showing a steering wheel according to a firstembodiment of the present invention;

FIG. 2 is a cross sectional view taken along line II—II shown in FIG. 1and showing a ring portion according to the embodiment of the presentinvention;

FIG. 3 is a cross sectional view taken along line III—III shown in FIG.1 and showing the ring portion according to the embodiment of thepresent invention;

FIG. 4 is a cross sectional view taken along line IV—IV shown in FIG. 1and showing the ring portion according to the embodiment of the presentinvention;

FIG. 5 is a plan view showing a state in which a soft portion and anextended portion are provided for the core metal of the ring portionaccording to the embodiment by molding;

FIG. 6 is a cross sectional view showing a ring portion according to amodification to the first embodiment;

FIG. 7 is a plan view showing a steering wheel according to a secondembodiment of the present invention;

FIG. 8 is a cross sectional view taken along line VIII—VIII shown inFIG. 7;

FIG. 9 is a cross sectional view taken along line IX—IX shown in FIG. 7;

FIG. 11 is a cross sectional view taken along line XI—XI shown in FIG.7;

FIG. 12 is a plan view showing a state in which a hard coating portionhas been formed around the core metal of the ring portion according tothe embodiment by injection molding;

FIG. 13 is a schematic cross sectional view showing a mold for use inthe foregoing embodiment;

FIG. 14 is a schematic cross sectional view showing another example ofthe mold according to the embodiment;

FIG. 15 is a an alternative cross sectional view taken along line XI—XIshown in FIG. 7;

FIG. 16 is an enlarged cross sectional view showing the surface of thebody of a hard portion serving as a coating layer according to theembodiment;

FIG. 17 is a plan view showing a state in which the body of the hardportion serving as a coating layer has been formed around the core metalof the ring portion according to this embodiment by injection molding;

FIG. 18 is a schematic view showing another example of the mold for usein the embodiment;

FIG. 19 is a cross sectional view showing a burr-removing portion of themold shown in FIG. 18;

FIG. 20 is a an alternative cross sectional view taken along line XX—XXshown in FIG. 19;

FIG. 21 is a an alternative cross sectional view taken along lineXXI—XXI shown in FIG. 19;

FIG. 23 is a cross sectional view showing the burr-removing portion ofthe mold according to another embodiment;

FIG. 24 is a an alternative cross sectional view taken along lineVIII—VIII shown in FIG. 7;

FIG. 25 is a an alternative cross sectional view taken along line XI—XIshown in FIG. 7;

FIG. 26 is an enlarged cross sectional view showing a modification of aportion adjacent to an end of a leather portion according to theembodiment;

FIG. 27 is an enlarged cross sectional view showing another modificationof a portion adjacent to the end of the leather according to theembodiment;

FIG. 28 is partial plan view showing a ring portion according to aconventional example; and

FIG. 29 is a cross sectional view taken along line XXIX—XXIX shown inFIG. 28.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention will now be described withreference to FIGS. 1 to 5. As shown in FIG. 1, a steering wheel Waccording to this embodiment incorporates an annular ring portion Rwhich is held when steering is performed; a boss portion B disposed inthe central portion of the ring portion R; and four spokes S forconnecting the ring portion R and the boss portion B to each other. Eachof the foregoing portions has a core metal 110 for establishing theconnections.

The core metal 110 incorporates a boss-portion core metal ill providedfor the boss portion B; a spoke-portion core metal 112 provided for eachspokes S; and a ring-portion core metal 113 provided for the ringportion R. The core metal 110 is structured such that a boss 111 a inthe central portion of the boss-portion core metal 111 which isconnected to a steering shaft of a vehicle (not shown) is made of steel.On the other hand, a boss plate 111 b, a spoke-portion core metal 112and a ring-portion core metal 113 around the boss 111 a are made ofdie-cast metal, such as an aluminum alloy. The ring-portion core metal113 has an inverted U-shape cross sectional shape, as shown in FIGS. 2and 3.

As shown in FIG. 1, hard portions 115F and 115B are bonded to front andrear portions of the ring portion R in the direction of the vehicle. Onthe other hand, soft portions 119R and 119L made of urethane or the likeand formed by injection molding (reaction injection molding included)are disposed in the right and left portions of the ring portion R in thelateral direction of the vehicle.

Each of the hard portions 115F and 115B disposed in front of the ringportion R and in the rear of the same is, as shown in FIGS. 2 and 4,composed of an upper split member 115 a having an inverted U-shape crosssectional shape and a lower split member 115 b having a U-shape crosssectional shape, the upper split member 115 a and the lower split member115 b being divided in the vertical direction. The split members 115 aand 115 b respectively incorporate bases 211, 212 disposed in the insideportion and made of epoxy resin or the like; and decorative portions210, 213 having a structure that a natural wood having a woodgrainfinish is coated with predetermined protective coating layer. Each ofthe split members 115 a and 115 b is manufactured by previously formingthe decorative portions 210, 213 to correspond to the shape of the ringportion R in which each of the split members 115 a and 115 b is disposedand by introducing the decorative portions 210, 213 into an injectionmolding mold for molding the bases 211, 212. After the mold has beenclosed, a material for molding the bases 211, 212 is injected into acavity to manufacture the split members 115 a and 115 b.

As shown in FIG. 4, ends of the bases 211, 212 of each of the splitmembers 115 a and 115 b adjacent to the soft portions 119R and 119L haverecess grooves 211 a, 212 a for receiving an end 122 a of a leather 122to be described later, the recess grooves 211 a, 212 a being formed inthe cross-sectional circumferential direction of the ring portion R.

The soft portions 119R and 119L disposed on the right and left sides ofthe ring portion R softer than the hard portions 115F and 115B aredisposed to cover a region from the circumference portion of thering-portion core metal 113 to the ring portion R of the spoke-portioncore metal 112. As shown in FIGS. 2 and 4, this embodiment has thestructure that the leather 122 is sewed to the surface of each of thesoft portions 119R and 119L by using a sewing thread 123 at a positionadjacent to the boss portion B on the inside of the ring portion R.

Each leather 122 has a developed shape having sections which are capableof covering the upper and lower surfaces of each of the soft portions119R and 119L are connected at a position on the outer surface of thering portion R. An end 122 a of each leather 122 is, as shown in FIG. 4,bonded and wound around a core tube 124 made of a hard synthetic resin,such as annular ABS resin. Moreover, an adhesive agent 127 is employedto bond the end 122 a to the inner surfaces of the recess groove 211 a,212 a so that the end 122 a is disposed in the recess grooves 211 a, 212a of the hard portions 115 a and 115 b. The core tube 124 can be dividedinto a plurality of sections in the circumference direction.

As shown in FIGS. 2, 4 and 5, this embodiment has a structure thatextended portions 120F and 120B extending from the soft portion 119 aredisposed between the inner surfaces of the bases 211, 212 of the hardportions 115F and 115B and the ring-portion core metal 113. Thethickness of each of the front and rear extended portions 120F and 120Bis smaller than the thickness of each of the soft portions 119R and 119Lby a quantity corresponding to the thickness of the bases 211, 212 ofeach of the hard portions 115F and 115B. The extended portions 120F and120B are disposed to cover the overall cross-sectional circumference ofthe ring-portion core metal 113 for which the hard portions 115F and115B are provided. The extended portions 120F and 120B are made of thesame material as that of the soft portion 119. Simultaneously withmolding of the soft portion 119, the extended portions 120F and 120B aremolded.

The method of manufacturing the steering wheel W according to thisembodiment will now be described. A core metal 110 is previouslymanufactured. The core metal 110 is manufactured by introducing a boss111 a into a predetermined die-casting mold so that die-casting isperformed. Also the split members 115 a and 115 b of the front and rearhard portions 115F and 115B are previously molded by injection-moldingthe bases 211, 212 such that the decorative portions 210, 213 are placedas an insert.

The core metal 110 is introduced into the injection molding mold formolding the soft portion 119 and the extended portion 120. Then, themold is closed, and then a predetermined material for molding isinjected into a cavity. As shown in FIG. 5, the soft portion 119 and theextended portion 120 are formed by injection molding to cover thespoke-portion core metal 112 and the ring-portion core metal 113

Then, the molded members are released from the opened mold. Then, anadhesive agent is applied to the outer surface of each of the extendedportions 120F and 120B and the opposite surfaces of the split members115 a and 115 b. Thus, the split members 115 a and 115 b are bonded tothe outer surfaces of the extended portions 120F and 120B.

Then, the end 122 a of the leather 122, which is wound around the outersurface of each of the soft portions 119R and 119L, is bonded and woundaround the core tube 124. Then, an adhesive agent is applied to theouter surface of each of the soft portions 119R and 119L. Then, theleather 122 is wound while a sewing thread 123 is being used to sew theleather 122. Thus, the steering wheel W can be manufactured. The coretube 124 around which the end 122 a of the leather 122 have been woundis bonded to the inner surface of the recess grooves 211 a, 212 a asdescribed above.

When the steering wheel W is joined to the vehicle, a lower cover (notshown) for covering the lower portion of the boss portion B is joined.Then, the boss 111 a is joined to the steering shaft by using a nut.Then, a pad P for covering the upper surface of the boss portion B isjoined so that the manufactured steering wheel W is joined to thevehicle.

As described above, the steering wheel W according to this embodimentthe extended portions 120F and 120B extending from the soft portions119R and 119L are formed in the portions to which the hard portions 115Fand 115B are bonded. That is, when the soft portions 119R and 119L areprovided for a portion around the ring-portion core metal 113 bymolding, also the extended portions 120F and 120B are formed. If theextended portions 120F and 120B are deviated from the ring-portion coremetal 113, deviation of the hard portions 115F and 115B, which arebonded to the portion around the extended portions 120F and 120B, fromthe extended portions 120F and 120B can be prevented. Thus, the hardportions 115F and 115B can be provided for the ring portion R.

The extended portions 120F and 120B are, at positions around thering-portion core metal 113, molded integrally with the soft portions119R and 119L. Therefore, even if the extended portions 120F and 120Bare deviated from the ring-portion core metal 113, deviation from thesoft portions 119R and 119L in the planar circumferential direction ofthe ring portion R can be prevented. As a result, the soft portions 119Rand 119L and the hard portions 115F and 115B bonded to the positionsaround the extended portions 120F and 120B can be disposed in the planarcircumferential direction of the ring portion R without any deviation.

The steering wheel W according to this embodiment permits a structurethat the hard portions 115F and 115B bonded to the overallcross-sectional circumferential direction of the ring portion R and thesoft portions 119R and 119L formed to cover the ring-portion core metal113 by molding and softer than the hard portions 115F and 115B aredisposed in the planar circumferential direction of the ring portion R.Even in the foregoing case, formation of an unnecessary stepped portionbetween the hard portions 115F and 115B and the soft portions 119R and119L can be prevented. The position, at which the leather 122 and theouter surface of the hard portions 115F and 115B are formed, and theouter surface of the hard portions 115F and 115B can concentrically becontinued. As a result, the appearance of the ring portion R can beimproved.

The steering wheel W according to this embodiment has the structure thatthe soft portions 119R and 119L and the extended portions 120F and 120Bmade of the same material are disposed in the overall planarcircumferential direction of the ring portion R to cover thering-portion core metal 113. Therefore, removal of burrs of the softportions 119R and 119L can be omitted. As a result, the number ofman-hours for manufacturing the steering wheel W and the cost of thesame can be reduced.

The steering wheel W according to this embodiment has the structure thatthe core tube 124 is bonded to the inner surfaces of the recess grooves211 a, 212 a in a state in which the end 122 a of the leather 122 arewound around the hard core tube 124 so as to be joined into the recessgrooves 211 a, 212 a of each of the hard portions 115F and 115B.Therefore, sagging of the end 122 a of the leather 122 can be prevented.Moreover, if the leather 122 is contracted in the planar circumferentialdirection of the ring portion, the core tube 124 bonded to the insideportions of the recess grooves 211 a, 212 a holds the leather 122 tolimit the position. Therefore, movement of the end 122 a of the leather122 can be prevented. As a result, the appearance of the ends of theleather 122 can satisfactorily be maintained for a long time.

When the end 122 a of the leather 122 are wound around the hard coretube 124 so as to be introduced into the recess grooves 211 a, 212 a asis employed in this embodiment, introduction into large recess grooves211 a, 212 a is permitted as compared with a structure that the end 122a is directly introduced into a woodgrain groove provided for the hardportion 115. Moreover, rigidity can be imparted to the end 122 a.Therefore, the operation for joining the leather 122 can satisfactorilybe performed.

A process of the end 122 a of the leather 122 may be performed such thatthe recess grooves 211 a, 212 a are not provided for the hard portion115. Moreover, as shown in FIG. 6, the end 122 a are introduced andbonded to an annular groove 125 a provided for the hard core tube 125which can be decomposed in the circumference direction. Then, the coretube 125 are bonded to the bases 211, 212, the soft portion 119 and theextended portion 120 by using an adhesive agent 127 so as to dispose theleather 122. If the core tubes 124 and 125 can easily be bonded to thebases 211, 212 and the soft portion 119, a hard synthetic resin plate ora metal plate which can easily be deflected in the cross-sectionalcircumference direction of the ring portion R may be employed.

In this embodiment, the leather 122 is provided for the surfaces of thesoft portions 119R and 119L. The present invention may be applied to asteering wheel which does not incorporate the leather 122. In theforegoing case, the recess groove 211 a, 212 a are not required for thebases 211, 212.

In this embodiment, the hard portion 115F and 115B are structured intotwo-layer shape incorporating the bases 211, 212 and the decorativeportions 210, 213 disposed on the outer surface of the bases 211, 212and made of a natural wood material having a woodgrain finish. Thedecorative portions 210, 213 may have a structure that a protectivecoating layer is provided and a printed layer having a predeterminedpattern is provided. The hard portion 115 may be constituted by a singlelayer made of a woody material or a hard synthetic resin having aprotective layer. The hard portion 115 is not limited to the two splitmembers 115 a and 115 b. The hard portion 115 may be composed of threeor more split members.

In this embodiment, the soft portion 119 and the extended portion 120are formed by injection molding. If a mold can be employed to mold thesoft portion 119 and the extended portion 120 to cover the ring-portioncore metal 113, the soft portion 119 and the extended portion 120 may beformed by compression-molding or pouring as a substitute for theinjection molding (including reactive injection molding).

A second embodiment of the present invention will now be described withreference to FIGS. 7 to 10. As shown in FIG. 7, a steering wheel Waccording to this embodiment incorporates a ring portion R, a bossportion B and a spokes S. Each portion is provided with a steering-wheelcore metal 1 for establishing the connections among the portions. Thatis, as shown in FIGS. 7 and 10, the steering-wheel core metal 1incorporates a boss-portion core metal 2 provided for the boss portionB, a spoke-portion core metal 3 provided for each of spokes S and aring-portion core metal 4 provided for the ring portion R.

The steering-wheel core metal 1 is structured such that a boss 2 a inthe central portion of the boss-portion core metal 2 which is connectedto the steering shaft is made of steel. Moreover, the other portions,that is, a boss cover 2 b around a boss 2 a of the boss-portion coremetal 2, a spoke-portion core metal 3 and a ring-portion core metal 4are made of die-cast metal formed by die-casting using a light alloy,such as a magnesium alloy or an aluminum alloy.

The die-cast metal for forming the boss cover 2 b, the spoke-portioncore metal 3 and the ring-portion core metal 4 according to thisembodiment is an aluminum alloy having a coefficient of thermalexpansion of 23.5×10⁻⁶/° C.

As shown in FIG. 9, the ring-portion core metal 4 has an invertedU-shape cross sectional shape.

As shown in FIGS. 7 to 9, the ring portion R has two hard portions 6 (6Fand 6B) made of hard synthetic resin and soft portions 12 (12R and 12L)made of soft synthetic resin softer than the hard portions 6, the hardportions 6 and the soft portion 12 being alternately disposed around thering-portion core metal 4 in the planar circumferential direction of thering portion R. The hard portion 6 incorporates a body 7 (7F and 7B)which covers the ring-portion core metal 4 and which is made of hardsynthetic resin; and a decorative layer 10 provided for the outersurface of the body 7 and having a woodgrain finish printed by hydraulicpressure transfer. The soft portion 12 incorporates a soft-portion body13 which covers the ring-portion core metal 4 and which is made of softsynthetic resin; and a leather 14 sewed to the outer surface of thesoft-portion bodies 13.

In this embodiment, the decorative layer 10 extends to a portion aroundthe ring-portion core metal 4 as well as the body 7 of the hard portion6 to easily perform the manufacturing process.

In this embodiment, the hard-portion bodies 7 are made of polypropylenehaving a coefficient of thermal expansion of 17.7×10⁻⁵/° C., while thesoft-portion bodies 13 are made of foamed urethane.

In this embodiment, the hard portion 6 is disposed in front of the ringportion R in a direction in which the vehicle is steered straight and inthe rear of the same. The soft portion 12 is disposed on the right andleft of the ring portion R in the direction in which the vehicle issteered straight. Moreover, the soft portions 12 extend to the positionof the right and left spokes S adjacent to the ring portion R.

Each leading end of the bodies 7 of the hard portions 6F and 6B in theplanar circumferential direction of the ring portion R is provided witha support portion 9 having a woodgrain groove 8 and arranged to supporta leather end 14 a of the leather 14, as shown in FIGS. 7 and 8. Each ofthe support portions 9 incorporates a support surface 9 a formed into acylindrical shape and arranged to be brought into contact with thereverse side of the leather 14 to support the leather end 14 a; and atapered portion 9 b tapered toward the leading end.

The woodgrain groove 8 is formed into an annular shape in thecross-sectional circumferential direction of the hard-portion body 7 toreceive each end 14 b of the leather 14.

The leathers 14 are, as shown in FIG. 9, sewed on the inside of the ringportion R adjacent to the boss portion B by using a sewing thread 15.

The process for manufacturing the steering wheel W according to thisembodiment will now be described. The steering-wheel core metal 1 ispreviously manufactured. The steering-wheel core metal 1 is manufacturedsuch that the boss 2 a is introduced into a predetermined die-castingmold to die-cast the steering-wheel core—metal 1. The die-caststeering-wheel core metal 1 is in a state shown in FIG. 10.

Then, the steering-wheel core metal 1 is introduced into a mold formolding the hard-portion bodies 7, and then the mold is closed. Then,the material for molding the body 7 is injected so that the body 7having the woodgrain groove 8 and the support portion 9 is molded.

Then, the member is released from the mold for molding the hard-portionbody 7. Then, the boss-portion core metal 2 of the steering-wheel coremetal 1 is masked. Then, the decorative layer 10 is provided for aportion including the woodgrain grooves 8 of the hard-portion bodies 7except for the boss-portion core metal 2 by hydraulic pressure transfer.

Then, the making material is removed, and then the steering-wheel coremetal 1 having the hard portions 6 is introduced into the mold formolding the soft-portion bodies 13. Then, the mold is closed, and thenthe material for molding the soft-portion body 13 is injected so thatthe soft-portion bodies 13 are molded. The mold surface of the mold formolding the soft-portion body 13 presses the outer surface of thesupport surface 9 a of the support portion 9 of the hard-portion body 7when the mold has been closed.

Then, the soft-portion body 13 is released from the mold, and then theleather 14 is sewed to each of the soft-portion bodies 13. At this time,the end 14 b is introduced into the woodgrain groove 8 provided for thehard-portion body 7 while the end 14 a of the leather 14 is beingbrought into contact with the outer surface of the support surface 9 aof the support portion 9 of the hard-portion body 7 such that thedecorative layer 10 is interposed. Then, the sewing thread 15 is used toprovide the leathers 14 for the soft portions 12. If necessary, anadhesive agent for bonding leather may be applied to the tapered portion9 b and the soft-portion body 13 when the leather 14 is sewed.

Then, a lower cover and a pad P (not shown) are joined to the lower andupper portions of the boss portion B so that the steering wheel W ismanufactured. The steering wheel W can be joined to the vehicle. Whenthe steering wheel is joined to the vehicle, the steering wheel W issecured to the steering shaft with a nut. Therefore, the steering wheelW is joined to the vehicle in a state in which the pad P has beenremoved. Then, the pad P is joined after the steering wheel W has beenjoined.

The steering wheel W according to this embodiment incorporates thering-portion core metal 4 made of-die-cast metal which is an aluminumalloy. The coefficient of thermal expansion of the ring-portion coremetal 4 is two times or more the coefficient of thermal expansion of aconventional steel pipe (the conventional steel pipe has a coefficientof thermal expansion of 12.1×10⁻⁶/° C., while the aluminum alloy has acoefficient of thermal expansion of 23.5×10⁶/° C.). Therefore, thecoefficient of thermal expansion of the ring-portion core metal 4 isclose to the coefficient of thermal expansion of the hard-portion body 7constituting the hard portion 6 and made of the hard synthetic resin(polypropylene has a coefficient of thermal expansion of 17.7×10⁻⁵/°C.). Therefore, if the steering wheel W is allowed to stand in the cabinof a vehicle, the temperature of which is raised considerably, the hardportion 6 cannot easily be cracked. Moreover, no influence is exerted onthe decorative layer 10 of the ring portion R. Therefore, thedurability, and more particularly, weather resistance can be improved.

The steering wheel W according to this embodiment incorporates thering-portion core metal 4 which has the inverted U-shape cross sectionto have a large surface area. Therefore, the ring-portion core metal 4easily absorbs heat conducted from the hard portion 6. Moreover,absorbed heat can easily be conducted from the ring-portion core metal 4to the steering shaft and the like through the spoke-portion core metal3 and the boss-portion core metal 2 so that the temperature of the hardportion 6 is easily lowered. As a result, thermal expansion of the hardportion 6 can be prevented. Thus, cracks of the hard portion 6 canfurthermore easily be prevented.

The ring-portion core metal 4 according to this embodiment is made ofthe aluminum alloy having a thermal conductivity (at 20° C.) of 0.53cal·cm⁻¹·s⁻¹° C.⁻¹ which is larger than the thermal conductivity (0.18cal·cm⁻¹·s⁻¹° C.⁻¹) of the conventional steel pipe. Therefore, heat ofthe hard portion 6 can furthermore easily be dispersed. Therefore, theforegoing effect can be enhanced.

Hence it follows that the steering wheel W according to this embodimentpermits the structure that the ring portion R is constituted bydisposing the hard portion 6 made of the hard synthetic resin and thesoft portion 12 made of the soft synthetic resin softer than the hardportion 6 around the ring-portion core metal 4 in the planarcircumferential direction of the ring portion R. If the foregoingstructure is employed, formation of a crack of the hard portion 6 can beprevented.

In this embodiment, the ring-portion core metal 4 is made of die-castmetal obtained by die-casting the aluminum alloy. When die-cast metalhaving a coefficient of thermal expansion of 20×10⁻⁶/° C. or larger isemployed to constitute the ring-portion core metal 4, the coefficient ofthermal expansion of the ring-portion core metal 4 can be made to beabout two times or more the coefficient of thermal expansion of theconventional steel pipe because the conventional steel pipe has acoefficient of thermal expansion of 12.1×10⁻⁶/° C. Therefore, thecoefficient of thermal expansion of the ring-portion core metal 4 can bemade closer to the coefficient of thermal expansion of the hard-portionbody 7. Therefore, if the steering wheel is allowed to stand in a cabinof a vehicle, the temperature of which is raised considerably, the hardportion cannot easily be cracked.

Therefore, other die-cast metal may be employed, for example, amagnesium alloy having a coefficient of thermal expansion of 26.0×10⁻⁶/°C. may be employed. The magnesium alloy has a thermal conductivity (20°C.) of 0.38 cal·cm⁻¹·s⁻¹° C.⁻¹ which is larger than the thermalconductivity (0.18 cal·cm⁻¹·s⁻¹° C.⁻¹) of the steel pipe. Therefore, thering-portion core metal 4 may be constituted by die-casting using themagnesium alloy.

It is preferable that the thermal conductivity (at 20° C.) of theemployed die-cast metal is 0.30 cal·cm⁻¹·s⁻¹° C.⁻¹ or greater.

In this embodiment, the hard portion 6 incorporates the body 7 and thedecorative layer 10 for coating the body, the decorative layer 10 beingformed by printing process of hydraulic pressure transfer. Apredetermined coating material may be applied to the body 7 to form thedecorative layer 10. An individual decorative material, such as a woodymaterial, may be bonded to the outer surface of the hard-portion body 7to form the decorative layer 10. The hard portion 6 may be constitutedby only the body 7 which does not have the decorative layer 10.

Similarly, in this embodiment, the soft portion 12 incorporates the body13 and the leather 14 for covering the body 13. The soft portion 12 maybe constituted by only a body 13 which does not have the leather 14.

The ring portion R according to this embodiment incorporates two hardportions 6 and two soft portions 12. The number of each of the hardportion 6 and the soft portion 12 maybe one or three if the hard portion6 and the soft portion 12 are disposed in the planar circumferentialdirection of the ring portion R. The foregoing numbers may arbitrarilybe determined to correspond to the number of the spokes S or the like.

In the foregoing embodiment, the right and left soft portions 12R and12L have the same volumes.

On the other hand, the front and rear hard portions 6F and 6B accordingto this embodiment are structured such that the volume of the front hardportion 6F is larger than that of the rear hard portion 6B.

A mold 20 for injection-molding each of the hard portions 6F and 6B willnow be described. As shown in FIG. 13, the mold 20 incorporates twosplit molds 21 and 22 which are opened in the vertical direction of thesteering wheel W. The split molds 21 and 22 incorporate molding surfaces21 a, 21 b, 22 a and 22 b for forming cavities 20 a and 20 c which areable to mold the hard portions 6F and 6B after the mold has been closed.Molding surfaces 21 a and 22 a mold the front hard portion 6F, whilemolding surfaces 21 b and 22 b mold the rear hard portion 6B.

The upper split mold 21 has a nozzle touch 20 e into which a nozzle ofan injection molding machine is inserted. One sprue 20 f is allowed tocommunicate with the nozzle touch 20 e. Moreover, runners 20 g and 20 hallowed to communicate with the gates 20 b and 20 d for injecting thematerial for molding into the cavities 20 a and 20 c are allowed tocommunicate with the one sprue 20 f.

To make time required to complete injection of the material for moldinginto each of the cavities 20 a and 20 c to be substantially the same,this embodiment is structured such that the resistance of the materialfor molding which is allowed to pass through the runners 20 g and 20 his changed to be inversely proportional to the volumes of the hardportions 6F and 6B. Specifically, as shown in FIGS. 12 and 13, theresistance of the material for molding which passes through the runner20 g for molding the hard portion 6F having the large volume is made tobe lower by shortening the length of the runner 20 g and by enlargingthe cross sectional area of the opening. To make the resistance of thematerial for molding which passes through the runner 20 h for moldingthe hard portion 6B having the small volume to be high, the runner 20 hhas a long length and a small cross sectional area of the openingthereof.

Each of gates 20 b and 20 d for injecting the material for molding thehard portions 6F and 6B into the cavities 20 a and 20 c is opened ineach of the support portions 9 which are the ends in the planarcircumferential direction of the ring portion of the hard portions 6Fand 6B, as indicated with alternate long and two short dashes linesshown in FIG. 12. Each of the gates 20 b and 20 d is opened above thering-portion core metal 4 to cause the material M for molding introducedinto the cavities 20 a and 20 c to flow along the upper surface 4 f (seeFIGS. 9 and 11) of the ring-portion core metal 4.

The split mold 21 has a set pin 20 i to be engaged to the boss 2 a ofthe steering-wheel core metal 1.

A method of manufacturing the steering wheel W by using the mold 20 willnow be described. As described above, the steering-wheel core metal 1 ispreviously manufactured.

Then, the boss 2 a is engaged to the set pin 20 i of the opened mold 20so that the steering-wheel core metal 1 is introduced into the splitmold 21. Then, the mold is closed to inject the material M for moldingthe bodies 7 of the hard portions 6F and 6B into the cavities 20 a and20 c from the injection molding machine through the sprue 20 f and therunners 20 g and 20 h. Thus, the bodies 7 of the hard portions 6F and 6Bhaving the woodgrain groove 8 and the support portion 9 are collectivelymolded.

At this time, the resistance of the material M for molding which passesthrough the runner 20 g is low and the resistance of the material M formolding which passes through the runner 20 h is high. Therefore, timerequired to complete injection of the material M for molding into themold 20 for molding the body 7 of the hard portion 6F having the largevolume can be shortened. On the other hand, time required to completeinjection of the material M for molding into the cavity 20 c for moldingthe body 7 of the hard portion 6B having the small volume can beelongated. Therefore, time required to complete injection of thematerial M for molding into the cavities 20 a and 20 c can be made to besubstantially the same.

Therefore, the operation of the injection molding machine can beinterrupted to correspond to the time required to complete theinjection. When the operation of the injection molding machine has beeninterrupted, the injecting pressure is not applied to the inside portionof each of the cavities 20 a and 20 c. Therefore, formation of burrs inthe vicinity of each of the hard portions 6F and 6B can be prevented.

In this embodiment, the material M for molding injected into thecavities 20 a and 20 c through the gates 20 b and 20 d conflicts withthe upper surface 4 f of the ring-portion core metal 4 so that thematerial M for molding flows along the upper surface 4 f. Then, thematerial M for molding is charged by a certain quantity in the portionadjacent to the upper surface 4 f. Then, the material M for moldingflows toward the lower surface of the ring-portion core metal 4.Therefore, formation of a weld mark on the upper surface of thering-portion core metal 4 can be prevented.

Then, the mold is opened, and then an operation for removing burrs isperformed. Then, the boss-portion core metal 2 of the steering-wheelcore metal 1 is masked to form the decorative layers 10 in the portionincluding the bodies 7 of the hard portions 6F and 6B except for theboss-portion core metal 2 by hydraulic pressure transfer.

Then, the mask material is removed, and then the steering-wheel coremetal 1 having the hard portions 6F and 6B is introduced into the moldfor molding the soft-portion body 13. Then, the mold is closed, and thenthe material for molding the soft-portion body 13 is injected so thatthe soft-portion bodies 13 of the soft portions 12R and 12L are molded.The surface of the mold for molding the soft-portion body 13 is broughtto a state in which the surface presses the outer surface of the supportsurface 9 a of the support portion 9 of the hard portion 6.

Then, the soft-portion body 13 is released from the mold, and then theoperation for removing burrs is performed. Then, the leather 14 is sewedto a portion around each soft-portion body 13. At this time, the end 14b is engaged to the woodgrain groove 8 provided for the hard portion 6while the leather end 14 a of the leather 14 is being brought intocontact with the outer surface of the support surface 9 a of the supportportion 9 of the hard portion 6 through the decorative layer 10. Then,the sewing thread 15 is used to locate the leathers 14 to the positionof the soft-portion body 13. If necessary, an adhesive agent for bondingleather may be applied to the tapered portion 9 b and the soft-portionbody 13 when the soft-portion body 13 is sewed.

The above-mentioned method of manufacturing the steering wheel Waccording to this embodiment is structured such that time required tocomplete injection of the material M for molding into the cavities 20 aand 20 c of the mold 20 for molding the hard portions 6F and 6B are madeto be substantially the same when the hard portions 6F and 6B are moldedwhich are sectioned and which have different volumes. Since the hardportions 6F and 6B are molded as described above, the operation of theinjection molding machine can be interrupted to correspond to the timerequired to complete the injection. When the operation of the injectionmolding machine is interrupted, no injection pressure is applied to eachof the cavities 20 a and 20 c. Therefore, formation of burrs in thevicinity of the hard portions 6F and 6B can be prevented. As a result,the operation for removing burrs which is performed after the moldingprocess has been completed can be facilitated.

The resistance of the material M for molding which passes through therunners 20 g and 20 h for molding the hard portions 6F and 6B is changedto be inversely proportional to the volumes of the hard portions 6F and6B. In this embodiment, the foregoing change is realized by adjustingthe lengths and the cross sectional areas of the openings of the runners20 g and 20 h. Only the lengths of the runners 20 g and 20 h may beadjusted or only the cross sectional areas of the openings of therunners 20 g and 20 h may be adjusted.

When the cross sectional areas of the openings of the runners 20 g and20 h are adjusted, the cross sectional areas of the openings areunformed for the overall lengths in this embodiment. As an alternativeto this, one or a plurality of weirs or the like may partially beprovided to reduce the cross sectional areas of the runners 20 g and 20h. Thus, the resistance of the material M for molding which passesthrough each of the runners 20 g and 20 h is adjusted.

When time required to inject the material M for molding into each of thecavities 20 a and 20 b of the mold 20 for molding each of the hardportions 6F and 6B is made to be substantially the same, an accumulatingportion for accumulating the material for molding may be provided forthe runner 20 h for molding the hard portion 6B having the small volumeto mold the hard portions 6F and 6B.

That is, a mold 20A shown in FIG. 14 has a structure that anaccumulating portion 20 j is provided for the runner 20 h of the runners20 g and 20 h extending from one sprue 20 f to mold the hard portions 6Fand 6B. If the runners 20 g and 20 h have the same capacity, thecapacity of the accumulating portion 20 j is the difference between thevolume of the hard portion 6F and that of the hard portion 6B. As amatter of course, the capacity of the accumulating portion 20 j may bedetermined in consideration of the difference in the capacity if therunners 20 g and 20 h have different capacities. While changing theresistance of the material M for molding which passes through each ofthe runners 20 g and-20 h, also the accumulating portion 20 j may beprovided as is employed in the foregoing embodiment.

When the molding operation is performed by using the foregoing mold 20A,time required to complete injection of the material into the cavity 20 cfor molding the hard portion 6B having the small volume can be elongatedbecause the material for molding is accumulated in the accumulatingportion 20 j. Therefore, time required to complete injection of thematerial M for molding into the cavities 20 a and 20 c of the mold 20Acan be made to be substantially the same. Therefore, formation of burrsaround the hard portions 6F and 6B can be prevented similarly to theforegoing embodiment. As a result, an operation for removing burrs whichis performed after the molding process has been performed can easily beperformed.

In this embodiment, two hard portions 6F and 6B sectioned to havedifferent volumes are provided for the ring portion R. Three or morehard portions may be provided to correspond to the number of the spokesS of the steering wheel W. If a plurality of the hard portions have thesame volume, the present invention may be applied when some hardportions have difference in the volume. As a matter of course, thepresent invention may be applied if all of the hard portions havevolumes which are different from one another.

The cross sectional shape of the ring-portion core metal 4 will now bedescribed. As shown in FIG. 9 and 15, the cross sectional shape isformed such that the lower portion of the steering wheel W is opened byemploying an inverted U-shape cross section which has the right and leftside walls 4 a and the ceiling wall 4 c which connects the right andleft side walls 4 a to each other at the upper ends of the side walls. 4a. The foregoing cross sectional shape is determined in consideration ofthe draft when the die-cast operation is performed. That is, the innersurface 4 d of the cross sectional shape is opened downwards and theouter surface 4 e is narrowed upwards. Note that the angle of narrowingof the outer surface 4 e is a small angle of about 1°.

A casting mold for molding the steering-wheel core metal 1 incorporatestwo split molds which are opened in the vertical direction of thesteering wheel W. At the position for casting the ring-portion coremetal 4, split surface D (see FIG. 21) of the casting mold is locatedwith reference to the position of the lower end surface 4 b of each ofthe right and left side walls 4 a. The casting surface of the uppersplit mold is used to cast the outer surface 4 e of the right and leftside walls 4 a and the ceiling wall 4 c. The casting surface of thelower split mold is used to cast the lower end surface 4 b of the rightand left side walls 4 a and the inner surface 4 d of the side walls 4 aand the ceiling wall 4 c.

As described above, the hard portion 6 incorporates the body 7 and thedecorative layer 10 having the woodgrain finish printed on the outersurface of the body 7 by the hydraulic pressure transfer.

The detailed structure of the decorative layer 10 will now be described.As shown in FIG. 16, the decorative layer 10 incorporates a printedlayer 10 a having a thickness of 1 μm to 3 μm and having the woodgrainfinish pattern, a primer layer 10 b for improving adhesiveness betweenthe body 7 and the printed layer 10 a and a transparent glossy layer 10c applied to protect the printed layer 10 a and having a thickness of 10μm to 40 μm. The glossy layer 10 c is made of transparent polyurethaneand acrylic resin or polyester resin.

As an alternative to the mold 20 shown in FIGS. 13 and 14, anotherexample of the mold 20 shown in FIGS. 18 to 21 may be employed toinjection-mold each of the hard-portion bodies 7F and 7B of thehard-portion body 7. The molding surfaces 21 a and 22 a mold the fronthard-portion body 7F, while the molding surfaces 21 b and 22 b mold therear hard-portion body 7B. Each of the molding surfaces 21 a, 21 b, 22 aand 22 b has an annular split projection (no reference numeral is givenin the drawings) in which the woodgrain groove 8 can be formed.

Each of the split molds 21 and 22 has burr-removing surfaces 21 c and 22c formed continuously from molding surfaces 21 a, 21 b, 22 a and 22 bfor molding the hard-portion bodies 7F and 7B and arranged to press thering-portion core metal 4. The burr-removing molding surface 21 c of theupper split mold 21 is, as shown in FIGS. 19 and 21, structured toforcible be brought into contact with the outer surface 4 e of the twoside walls 4 a and the ceiling wall 4 c in the cross section of thering-portion core metal 4. The burr-removing molding surface 22 c of thelower split mold 22 incorporates a side end surface 22 d which canforcibly be brought into contact with the lower end surface 4 b of thetwo side walls 4 a and a side inner surface 22 e which is forciblybrought into contact with the inner surface 4 d of the two side walls 4a and the ceiling wall 4 c. Note that the side inner surface 22 e isprovided for the outer surface of the projection 22 f provided for theburr-removing portion Y.

As shown in FIGS. 19 and 20, the split surface 23 of the split molds 21and 22 is disposed in a portion adjacent to the molding portion 23 a formolding the hard-portion bodies 7F and 7B such that the draft of thehard-portion bodies 7F and 7B each having an eclipse cross sectionalshape and the intermediate position of the hard-portion bodies 7F and 7Bin the vertical direction is used as a reference. As shown in FIGS. 19and 21, the split surface 23 is disposed in the portion adjacent to thepressing surface 23 c of the burr removing surfaces 21 c and 22 c suchthat the position of the lower end surface 4 b of the two side walls 4 aon the cross section of the ring-portion core metal 4 is used as areference. Thus, the split surface 23 coincides with the split surface Dof the casting mold for molding the steering-wheel core metal

In the molding portion 23 a of the split surface 23, an inclined portion23 b moderately inclined from the intermediate position of thehard-portion bodies 7F and 7B in the vertical direction toward theburr-removing portion Y is provided for the position of each supportportion 9 of the hard-portion bodies 7F and 7B, as indicated with adashed line shown in FIG. 19. Thus, the inclined portion 23 b iscontinued from the molding portion 23 a of the molding surfaces 21 a, 21b, 22 a and 22 b to the pressing surface 23 c of the burr-removingsurfaces 21 c and 22 c.

Each of the gates 20 b and 20 d for injecting the material for moldingthe hard-portion bodies 7F and 7B which are the coating layers into thecavities 20 a and 20 c is formed in the leading end 9 c of the supportportion 9 which is the end in the planar circumferential direction ofthe ring portion of the hard-portion bodies 7F and 7B, as shown in FIGS.15, 17, 18 and 21.

The gates 20 b and 20 d are disposed in the upper portion of thesteering wheel W as compared with the molding portion 23 a of the splitsurface 23 for molding the hard-portion bodies 7F and 7B of the twosplit molds 21 and 22. In this embodiment, the gates 20 b and 20 d areformed toward the central portion O of the cross section of thering-portion core metal 4 and toward the position adjacent to theintersection between the side wall 4 a and the ceiling wall 4 c on thecross section of the ring-portion core metal 4 such that the angle θfrom the right and left positions is about 50°, the gates 20 b and 20 dbeing provided for the upper split mold 21. Elements having the samereference numeral as those shown in FIGS. 13 and 14 are omitted fromdescription.

A method of manufacturing the steering wheel W using the mold 20 shownin FIGS. 18 to 21 will now be described.

The process for molding the hard-portion bodies 7F and 7B is the same asthat shown in FIG. 13.

Therefore, formation of a weld mark of the hard-portion bodies 7F and 7Badjacent to the upper surface 4 f of the ring-portion core metal 4 canbe prevented.

The decorative layer 10 is formed by hydraulic pressure transfer. Thedecorative layer 10 is formed by applying the primer layer 10 b. Then,the printed layer 10 a is formed by the hydraulic pressure transfer, andthen the glossy layer 10 c is applied. Then, the foregoing process isperformed so that the hard portions 6F and 6B are formed.

The steering wheel W according to this embodiment incorporates thehard-portion bodies 7F and 7B which are coating layers which arepartially disposed in the planar circumferential direction of the ringportion are molded such that the positions of the gates 20 b and 20 dwhen the molding process is performed are higher than the position ofthe molding portion 23 a of the split surface 23 of the two split molds21 and 22. Therefore, the material M for molding flows along the uppersurface 4 f of the ring-portion core metal 4. Thus, the position atwhich the material M for molding is fused on the lower surface as asubstitute for the upper surface 4 f of the ring-portion core metal 4.Therefore, if the hard-portion bodies 7F and 7B serving as the coatinglayers are formed by injection molding by using one gate 20 b and 20 ddisposed adjacent to the ends of the hard-portion bodies 7F and 7B,formation of a weld mark of the hard-portion bodies 7F and 7B on theupper surface 4 f of the ring-portion core metal 4 can be prevented.

This embodiment permits a structure that the cross sectional shape ofthe ring-portion core metal 4 is formed into the inverted U-shape crosssectional shape to open the lower portion of the steering wheel suchthat the right and left side walls 4 a and the ceiling wall 4 c forconnecting the right and left side walls 4 a at the upper ends of theright and left side walls 4 a are provided. In the foregoing case, thematerial M for molding which has been injected into the cavities 20 aand 20 c through the gates 20 b and 20 d conflicts with the uppersurface 4 f of the ring-portion core metal 4. Thus, the material M formolding flows along the upper surface 4 f so that the material M formolding in a certain quantity is charged in the portion on the uppersurface 4 f. Then, the material M for molding flows along the lowersurface of the ring-portion core metal 4. Therefore, if the hard-portionbodies 7F and 7B serving as the coating layers are partially providedfor the portion around the ring-portion core metal 4 having the invertedU-shape cross sectional shape, formation of a weld mark of thehard-portion bodies 7F and 7B on the core-metal upper surface 4 f can beprevented. As a result, defective appearance of the hard-portion bodies7F and 7B can be prevented.

As an alternative to the structure of this embodiment in which thering-portion core metal 4 has the inverted U-shape cross sectionalshape, the ring-portion core metal 4 may be constituted by a steel pipeor a steel rod to have a circular cross sectional shape or an eclipsecross sectional shape. In the foregoing case, the arrangement of theforegoing embodiment in which the gates 20 b and 20 d are disposed suchthat the material M for molding flows along the core-metal upper surface4 f is able to prevent formation of a weld mark on the upper surface 4 fof the ring-portion core metal 4.

It is preferable that the positions of the gates 20 b and 20 c forcausing the material M for molding to flow along the core-metal uppersurface 4 f to prevent formation of the weld mark on the core-metalupper surface 4 f are determined such that angle θ with respect to thecenter O of the cross section of the core metal 4 is 5° to 175°including the upper position. If the angle is smaller than 5° or if theangle is larger than 175°, the material M for molding first flows to thelower surface of the core metal 4. Thus, there is apprehension that aweld mark is formed on the core-metal upper surface 4 f.

When the ring-portion core metal 4 is formed to have the invertedU-shape cross sectional shape, this embodiment attains the followingoperation and effect. That is, if the material M for molding is firstinjected to the position adjacent to the inner surface 4 d of the coremetal 4, the material M for molding upwards pushes the ring-portion coremetal 4. Thus, deviation of the ring-portion core metal 4 undesirablyoccurs. In this embodiment, the material M for molding is injectedthrough the gates 20 b and 20 d formed above the ring-portion core metal4 to downwards push the ring-portion core metal 4. Therefore, upwardpushing of the ring-portion core metal 4 can be canceled so thatdeviation and deformation of the ring-portion core metal 4 areprevented.

In this embodiment, the thin printed layer 10 a formed by hydraulicpressure transfer is interposed on the surface of the hard-portionbodies 7F and 7B serving as the coating layers to form a glossy coatingfilm (the glossy layer 10 c) Since no weld mark is formed on thehard-portion bodies 7F and 7B on the upper surface 4 f of the core metal4, deterioration in the appearance of the hard portions 6 of the ringportion R can be prevented.

In this embodiment, the glossy coating film 10 c is provided for thesurface of each of the hard-portion bodies 7F and 7B serving as thecoating layers. As a matter of course, the hard portion 6 may beconstituted by only the hard-portion bodies 7F and 7B.

In this embodiment, the split surface 23 of the mold 20 is made coincidewith the split surface D of the casting mold for casting thering-portion core metal 4 at the burr-removing portion Y at the end inthe planar circumferential direction of the ring portion in thehard-portion bodies 7F and 7B serving as the coating layers.

Therefore, in the burr-removing portion Y, the burr-removing moldingsurface 22 c of the lower split mold 22 is forcibly brought into contactwith only the lower end surface 4 b of the two side walls 4 a of thering-portion core metal 4 and the inner surface 4 d of the side walls 4a and the ceiling wall 4 c. The burr-removing molding surface 21 c ofthe upper split mold 21 is forcibly brought into contact with only theouter surface 4 e of the two side walls 4 a and the ceiling wall 4 c ofthe ring-portion core metal 4. Thus, locating along the draft of thering-portion core metal 4 can easily be performed.

As a result, when the mold 20 is closed, the burr-removing surfaces 21 cand 22 c of the upper and lower split molds 21 and 22 are able tocompletely press the overall circumference of the ring-portion coremetal 4 in the burr-removing portion Y. As a result, removal of burrscan easily be performed.

When the cross sectional shape of the ring-portion core metal 4 which ismolded by die-casting is formed into the inverted U-shape crosssectional shape, a portion adjacent to the intermediate portion in thevertical direction of the outer surface of the right and left side walls4 a is gradually expanded as shown in FIGS. 22 and 23. When thesteering-wheel core metal 1 is die-cast, the split surface 23 of themolds 20A and 20B is made coincide with the split surface D of thecasting mold for casting the ring-portion core metal in theburr-removing portion Y at the end in the planar circumferentialdirection of the ring portion of the hard-portion body 7. Moreover, thesplit surface 23 is disposed at the position of the right and left sidewalls at which the maximum expansion is realized. Thus, removal of burrscan easily be performed.

In this embodiment, the ring-portion core metal 4 which is molded bydie-casting has the inverted U-shape cross sectional shape. Thering-portion core metal 4 may be die-cast to have another crosssectional shape. Also in the foregoing case, the split surface of themolds at the burr-removing position is made coincide with the splitsurface of the casting mold for casting the ring-portion core metal.Thus, removal of burrs of the coating layer can easily be performed.

An example is shown in FIGS. 24 to 26 in which the leather 14 is bondedto the surface of each of the soft-portion bodies 13 by the adhesiveagent 16. Moreover, the sewing thread 15 is used to sew the leather 14on the inside of the ring portion R adjacent to the boss portion B.

In this embodiment, a transparent coating layer 30 having a thickness of10 μm to 40 μm and arranged to protect the printed layer 10 a is formedon the outer surface of the decorative layer 10. As shown in FIGS. 24and 26, the coating layer 30 is, together with the decorative layer 10,extended to the inner surface of the woodgrain groove 8 and the outersurface of the support portion 9 including the tapered portion 9 b aswell as the surface of the body 7. In this embodiment, the coating layer30 and the decorative layer 10 are extended to the end surface of thesupport portion 9 and the outer surface of the ring-portion core metal4.

The coating layer 30 according to this embodiment is made ofpolyurethane to realize satisfactory adhesiveness between the leather 14and the soft-portion body 13 made of soft polyurethane.

The steering wheel W according to this embodiment is manufactured by amethod similar to the above-mentioned method.

In this embodiment, the hard portions 6 are molded, and then releasedfrom the mold for molding the hard portions 6. Then, the boss-portioncore metal 2 of the steering-wheel core metal 1 is masked to form theprimer layer 10 b on the outer surface of the hard portions 6 and theouter surface of the ring-portion core metal 4 except for theboss-portion core metal 2 by coating. Then, hydraulic pressure transferis performed to transfer the printed layer 10 a. Then, the coating layer30 is formed on the outer surface of the printed layer 10 a by coating.

Then, the mask is removed, and then the steering-wheel core metal 1having the hard portions 6 is introduced into the mold for molding thesoft-portion bodies 13. Then, the mold is closed, and then the materialfor molding the soft-portion bodies 13 is injected. Thus, thesoft-portion bodies 13 are molded. The molding surface of the mold formolding the soft-portion bodies 13 is brought to a state in which themolding surface presses the outer surface of the support surface 9 a ofthe support portion 9 of the hard-portion body 7 after the mold has beenclosed.

Then, the soft-portion bodies 13 are released from the mold for moldingthe soft-portion bodies 13. Then, the chloroprene adhesive agent 16 isapplied to the soft-portion bodies 13 and the portion around the supportportion 9. Then, the leather 14 is sewed. At this time, the ends 14 bare engaged to the woodgrain groove 8 provided for the hard-portion body7 while the ends 14 a of the leather 14 are being brought into contactwith the outer surface of the support surface 9 a of the support portion9 of the hard-portion body 7 through the adhesive agent 16. Then, thesewing thread 15 is used to dispose the leather 14 in the region fromthe outer surface of the soft-portion body 13 to the woodgrain groove 8of the hard portions 6.

The steering wheel W according to this embodiment has the structure thatthe coating layer 30 for covering the hard portions 6 is applied to theouter surface of the support portion 9 including the tapered portion 9 bso that the soft-portion body 13 and the leather 14 are bonded to thehard portion 6.

That is, the ends 14 a of the leather 14 are bonded to the supportportion 9 of the hard portion 6 such that the coating layer 30 is usedas the primer layer of the adhesive agent 16. Therefore, separation fromthe support portion 9 of the hard portion 6 can be prevented. Hence itfollows that the ends 14 a can firmly be bonded to the support portion 9of the hard portion 6. As a result, occurrence of a defective appearanceof the ring-portion R can be prevented even after use for a long time.

The coating layer 30 serving as the primer layer for the leather 14 isformed as surface treatment of the hard portion 6. Therefore, thecoating layer 30 can be formed by simply applying to be extended. As aresult, the number of man-hours and the manufacturing cost of thesteering wheel W can be reduced.

Also the coating layer 30 is applied to the tapered portion 9 b formedapart from the inner surface of the leather 14 in the support portion 9and projecting into the inner surface portion of the soft portion 12 aswell as the support surface 9 a of the support portion 9 of the hardportion 6 for supporting the leather 14. In the foregoing case, thecoating layer 30 serves as an adhesive agent for directly bonding thesoft portion 12 to the support portion 9 of the hard portion 6.

Therefore, contraction of the molded soft-portion body 13 can beprevented. As a result, separation of the soft portion 12 from the hardportion 6 and the ring-portion core metal 4 can be prevented. Hence itfollows that deterioration in the tough required when the leather 14 isheld can be prevented.

In this embodiment, the tapered portion 9 b of the support portion 9 ofthe hard portion 6 is tapered toward the leading end. Therefore, thetouch when the portion adjacent to the ends 14 a of the leather 14 isheld is made such that the hardness is gradually raised toward thesupport surface 9 a of the hard portion 6. Thus, smooth touch can berealized. If the soft-portion body 13 is contracted and separated fromthe tapered portion 9 b, the touch undesirably deteriorates.

In this embodiment, the hard-portion body 7 is made of polypropylene. Asan alternative to this, ABS resin or polyester resin may be employed.

In this embodiment, the soft-portion body 13 is made of softpolyurethane. As an alternative to this, soft polyvinyl chloride orthermoplastic elastomer (polyester, polyurethane, polyamide, polyolefineor polystyrene) may be employed.

In this embodiment, the coating layer 30 is made of polyurethane. Ifsatisfactory adhesiveness is realized with the soft-portion body 13, andthe leather 14, polyester resin or acrylic resin may be employed.

In this embodiment, the coating layer 30 protects the decorative layer10 formed by hydraulic pressure transfer. A coating film in a specificcolor or having a decorative pattern may be provided for the surface ofthe hard-portion body 7 of the hard portion 6. As an alternative tothis, a coating layer 30 for a decorative member, such as a bonded woodymember, may be employed. The coating layer 30 directly applied to thehard-portion body 7 of the hard portion 6 to protect the body 7 ordecorating the same may as well as be applied to the support portion 9to serve as the adhesive agent for the leather 14 and the soft-portionbody 13.

In this embodiment, the coating layer 30 is as well as extended to thesurface of the ring-portion core metal 4 at the position at which thesoft-portion body 13 is disposed. In the foregoing case, theadhesiveness of the soft-portion body 13 with respect to thering-portion core metal 4 can be improved. Therefore, the operation forapplying the primer to the ring-portion core metal 4 which is performedbefore the soft portion 12 is molded can be omitted. Hence it followsthat the process for manufacturing the steering wheel W can furthermorebe simplified.

In this embodiment, the end 14 b of the leather 14 is engaged to thewoodgrain groove 8 of the hard portion 6. The coating layer 30 enlargesthe force for anchoring the ends 14 a to the support portion 9 of thehard portion 9. Therefore, as shown in FIG. 27, the woodgrain groove 8may be omitted. In the foregoing case, the end 14 b of the leather 14 isfolded back to use the coating layer 30 to bond the ends 14 a to thesupport portion 9 of the hard portion 6. Reference numeral 18 shown inFIG. 27 represents an accommodating recess provided for the hard portion6 to accommodate the end 14 b in order to prevent projection of the end14 b which is thickened owing to folding back.

As shown in FIG. 27, the coating layer 30 is extended to at least theouter surface of the support portion 9. That is, extension to the outersurface of the ring-portion core metal 4 is not required. Similarly, thedecorative layer 10 may be extended to the outer surface of the supportportion 9. Note that the decorative layer 10 maybe provided for only theouter surface of the hard-portion body 7 of the hard portion 6, as shownin FIG. 27.

The first and second embodiments have been described as individualembodiments. The two embodiments may be combined with each other ifpermitted. Note that the present invention is not limited to only theforegoing embodiments. A variety of modifications are permitted withinthe scope of the claims.

1. A steering wheel comprising: a core metal of a ring portion; at leastone molded soft portion covering a circumferential portion of the coremetal and the core metal of the ring portion; leather disposed on asurface of the at least one soft portion; at least one hard portioncovering circumferential portions of the core metal of the ring portionoutside the circumferential portions covered by the at least one softportion and being harder than the at least one soft portion; and at tosurround said core metal of said ring portion; and at least one extendedportion that is intergrally extended from the at least one soft portionto surround the core metal of the ring portion, wherein the at least onehard portion is for covering the at least one extended portion, and theleather extends in a circumferential direction beyond the edges of theat least one soft portion so as to overlap and attach to an edge regionof the at least one hard portion.
 2. A steering wheel according to claim1, wherein the at least one soft portion and the at least one extendedportion are molded simultaneously and are made of the same material. 3.A steering wheel according to claim 1, wherein the at least one softportion and the at least one extended portion cover an overall body ofthe core metal of the ring portion.
 4. A steering wheel according toclaim 1, wherein the at least one extended portion is thinner than theat least one soft portion by a thickness of the at least one hardportion.
 5. A steering wheel according to claim 1, wherein the at leastone hard portion incorporates an upper split member having an invertedU-shaped cross section and a lower split member having a U-shaped crosssection.
 6. A steering wheel according to claim 5, wherein an end of theleather is fixed around a core tube and ends of the upper split memberand the lower split member have recess grooves for receiving the end ofthe leather that is fixed around the core tube.
 7. A steering wheelaccording to claim 1, wherein an end of the leather is supported by asupport portion formed at an end of the at least one hard portion so asto be secured to the at least one hard portion, a coating layer isapplied to an outer surface of the support portion and to a surface ofthe at least one hard portion, and the at least one soft portion and theleather are bonded to the at least one hard portion through the coatinglayer.
 8. A steering wheel according to claim 7, wherein the supportportion is formed with a groove having an annular shape in the crosssectional circumferential direction of the at least one hard portion toreceive an end of the leather.
 9. A steering wheel according to claim 7,wherein the support portion further comprises: a support surface forsupporting the inner surface of the leather; and a tapered portionhaving a narrowed outer shape for facilitating a connection between theat least one hard portion and the at least one soft portion.
 10. Asteering wheel according to claim 7, further comprising an adhesivelayer that is applied to a surface of the at leant one soft portion andthat bonds the surface of the at least one soft portion to the leather.11. A steering wheel according to claim 10, wherein the leather isbonded to the support portion through the adhesive layer and the coatinglayer.
 12. A steering wheel according to claim 7, wherein a decorativelayer is disposed between a surface of the at least one hard portion andthe coating layer, the decorative layer includes a printed layer and aprimer layer that is disposed between the surface of the at least onehard portion and the printed layer, the decorative layer and the coatinglayer are applied to the outer surface of the at least one supportportion, and the at least one soft portion and the leather are bonded tothe at least one hard portion through the decorative layer and thecoating layer.
 13. A steering wheel according to claim 12, wherein thedecorative layer and the coating layer are also applied between at leasta portion of the core metal of the ring portion and the at least onesoft portion.
 14. A steering wheel according to claim 1, whereincircular grooves are formed radially outside the at least one extendedportion between the at least one hard portion and the at least one softportion for receiving a core tube with an end of the leather being fixedthereto, wherein the core tube is fixed to the at least one hardportion.
 15. A steering wheel according to claim 1, wherein the at leastone hard portion and the at least one soft portion are disposed in aplanar circumferential direction of the core metal of the ring portionand the core metal of the ring portion is of die-cast metal.
 16. Asteering wheel according to claim 15, wherein the die-cast metal has acoefficient of thermal expansion of 20×10⁻⁶/° C. or greater.
 17. Asteering wheel according to claim 16, wherein the die-cast metal is oneof an aluminum alloy and a magnesium alloy.
 18. A steering wheelaccording to claim 15, wherein the die-cast metal has a thermalconductivity of 0.30 cal·cm⁻¹·s⁻¹° C.⁻¹ or greater at 20° C.